1. Field of the Invention
The present invention generally relates to ceramics. More specifically, a method of improvement of ceramics in replacement components, such as components in hip and knee replacements.
2. Description of the Related Art
It's inevitable that all living things age overtime, so do the many components that make up the living things. Human beings are also living things and we have the ability to regenerate some of our components when they wear out or some of the components are just naturally replaced. For example, our skin cells are continuously replaced on a daily basis, hair cells are continuously added so that hair can grow, and calcium is continuously absorbed and reabsorbed in bone components. The absorption of calcium in the bones helps to strengthen them. However, because of aging, degenerative diseases, such as osteoporosis, or other causes, the bones can become fragile and break causing excruciating pain. In other cases, as in osteoarthritis, the cartilage becomes worn away and bone deformities develop. The load-bearing situation on bone-on-bone is very painful. In addition, primarily in younger patients, sports-related injuries can lead to severe damage to hips or knees, necessitating surgery.
For many years, man-made devices have been developed in order to help replace components that cannot be regenerated and are no longer functioning properly. Such man-made devices include biocompatible devices and materials. The devices include heart valves, pace makers, spinal, dental, or breast implants, collagen for soft tissue augmentation, and orthopedic devices, such as total knee and hip joint replacements.
Artificial joints can include a plastic-cup made of ultrahigh molecular weight polyethylene (UHMWPE) that is placed in a joint socket, a metal (titanium alloy or cobalt chromium alloy) or ceramic (aluminum oxide or zirconium oxide) ball that is complementary to the cup and is affixed to a metal stem. These artificial joints are used to replace hip, knee, shoulder, and other joints in order to restore function after degeneration, car and construction accidents, and sport injuries.
However, these artificial joints typically do not last, as long as needed, especially when the patient is young and can typically live longer due to medical advancements. Conventional artificial joints last about 10 years and need to be replaced due to wear and loosening. Additionally, due to localized stress from the interaction of the ball and socket, small particles can break off from the surface and contaminate the surrounding synovial fluid. The body's immune system will attempt to degrade the particles by secreting enzymes, which can kill the adjacent bone cells or cause osteolysis and lead to mechanical loosening and failure of the artificial joints. Further, despite the best efforts and techniques (including polishing), the surfaces of the balls can have protuberances, which through use can cause scratches that lead to microcracks in the balls and ultimately to catastrophic fracture of the ball and joint. These fractures can be extremely painful to the patients and require expensive replacements and surgery. The more expensive ceramic joint replacements are normally fitted in younger, more active patients, in the expectation that the life of the joint replacement will be longer than that of metallic components. This has too often not been the case, principally due to fracture of the more brittle ceramic.
Therefore, there is a need for a method and means to decrease particles in the synovial fluids caused by friction on the ceramics. There is also a need to prevent microcracks from starting or prevent the microcracks from increasing in size, thereby increasing the life of the ceramic prosthesis.